Jaundice Phototherapy Calculator

Newborn jaundice reflects a temporary mismatch between bilirubin production and clearance. Neonates have a short red cell lifespan and high turnover, while hepatic conjugation by the enzyme UGT1A1 is still immature and the gut reabsorbs bilirubin through the enterohepatic circulation. Total serum bilirubin therefore climbs after birth and peaks around day three to five in term infants. Because the threshold for harm depends on how many hours old the infant is rather than on the number alone, treatment decisions use hour-specific curves. Gestational age and risk factors shift those curves downward: isoimmune haemolytic disease, glucose-6-phosphate dehydrogenase deficiency, asphyxia, lethargy, temperature instability, sepsis, acidosis and serum albumin below about 3.0 g/dL all mark an infant whose free bilirubin can reach brain tissue at a lower total level. Multiply mg/dL by 17.1 to obtain micromol/L. Phototherapy works photochemically, not thermally. Light in the blue-green band, roughly 460 to 490 nm, is absorbed by bilirubin in the skin and converts it to configurational isomers and to lumirubin, a structural isomer that is water soluble and can be excreted in bile and urine without conjugation. Intensive phototherapy is conventionally defined as at least 30 micro-W per square cm per nm over that waveband delivered to the maximum body surface, which is why lamp type, spacing and how much of the infant is exposed matter as much as the decision to start. Exchange transfusion thresholds sit roughly 4 to 5 mg/dL above phototherapy thresholds. The thresholds implemented here follow the older simplified three-curve nomogram; the 2022 American Academy of Pediatrics revision raised most of them by about 2 mg/dL and uses separate curves for each gestational week from 35 to 40.

The therapy was discovered by observation rather than experiment. In the mid-1950s at Rochford General Hospital in Essex, England, a ward sister named J Ward noticed that jaundiced infants wheeled out into the sunlit courtyard lost their yellow colour, and that a sample of blood left on a windowsill in sunlight lost its pigment as well. Richard Cremer, P W Perryman and D H Richards followed the observation up and reported in The Lancet in 1958 that both sunlight and artificial blue light lowered serum bilirubin in newborns. Uptake outside Britain was slow and initially sceptical until Jerold Lucey and colleagues published a controlled trial in Pediatrics in 1968 showing the effect in premature infants, after which phototherapy replaced exchange transfusion as first-line treatment for most hyperbilirubinaemia. The mechanism was worked out over the following two decades, with structural isomerisation to lumirubin identified as the main route of elimination rather than simple photo-oxidation. Risk stratification came later. Vinod Bhutani and colleagues published an hour-specific bilirubin nomogram in Pediatrics in 1999 that allowed a predischarge measurement to be plotted against percentile risk zones for later severe hyperbilirubinaemia, which made universal predischarge screening practical. The American Academy of Pediatrics issued treatment thresholds in 1994, revised them substantially in 2004 for infants of 35 weeks gestation and above, and issued a further revision in 2022 that raised thresholds and refined them by gestational week in response to evidence that the earlier curves led to overtreatment.